Agrobacterium rhizogenes (Riker et al. 1930)
Conn 1942
Agrobacterium rhizogenes (Riker et al. 1930) Conn 1942 (Approved Lists 1980) emend. Sawada et al. 1993
Rhizobium rhizogenes (formerly Agrobacterium rhizogenes) is a
Gram-negative soil bacterium that produces hairy root disease in
dicotyledonous plants. R. rhizogenes induces the formation of proliferative multiple-branched adventitious roots at the site of infection, so-called 'hairy roots'.[3] It also induces
galls.[4]: 39
In the
rhizosphere, plants may suffer from wounds by soil
pathogens or other sources. This leads to the secretion of
phenolic compounds like
acetosyringone which have
chemotactic effects that attract the bacteria. Under such conditions, certain bacterial genes are turned on leading to the transfer of its
T-DNA from its root-inducing plasmid (Ri plasmid) into the plant through the wound. After integration and expression, in vitro or under natural conditions, the hairy root
phenotype is observed, which typically includes overdevelopment of a root system that is not completely
geotropic, and altered (wrinkled) leaf morphology, if leaves are present.[5]R. rhizogenes also propagates as a
seed-borne pathogen.[4]: 39
Bacterial genes may be retained within the plant,[6] and
sweet potato for instance has retained and actively expresses A. rhizogenes genes which are not present in other members of its genus.[7]
The
hairy roots are grown in vitro in
bioreactors to study their soil interaction with other pathogens like
fungi and
nematodes. This technique has also led to the commercial production of certain metabolic compounds that the plant is known to secrete, especially in regard to the medicinal plants that are difficult to cultivate in sufficient quantities by other means.[8] The root cultures are also used for
genetic engineering.[9][10]
References
^The Young paper renames on the ground of a
lumper view of Rhizobium that subsumes all of Agrobacterium, which also resolves much of the phylogenetic incoherences on the molecular level given 2001 data.
GTDB agrees on this assignment of the type strain, and finds that it's still coherent even if Agrobacteirum is not subsumed. However, GTDB makes 4 extra species-level clusters containing genomes likely mislabelled as this species.[2]